The House of Commons will break the law if it goes ahead with its plan to release only a heavily censored version of MPs' expenses claims, according to the leading barrister involved in a campaign to get the information published.

Hugh Tomlinson QC, who represented freedom of information campaigners in their long legal battle with parliament, says the redactions proposed by the Commons will breach existing court orders.

His comments mean yet further embarrassment to reputations in the Commons after one of the most damaging months in its history, with claims from more than 150 MPs revealed, and the Speaker, Michael Martin, forced from office.

Tomlinson's comments have led ­Geoffrey Robinson – a close ally of the prime minister – to write to Harriet ­Harman, the leader of the Commons, to demand a rethink on the redactions.

Details of all 646 MPs' expenses claims are due to be released in mid-July. They are currently being edited by the Commons authorities. But a computer disk obtained by the Daily Telegraph includes full, unedited details of the claims, including letters between MPs and the fees office.

The letters have produced some of the most embarrassing evidence for MPs, including details such as Douglas Hogg's apparent attempt to claim for the cleaning of his moat, the Tory MP John Maples' claim for expenses for his second home in his constituency through he stayed at a private members' club in London, and the culture secretary Andy Burnham's appeal saying his expenses needed to be paid promptly otherwise he "might be in line for divorce".

But the Commons has been allowing MPs to make redactions according to ­criteria agreed by the members' estimate committee, a cross-party MPs' group.

According to Tomlinson, from Matrix Chambers, if such letters are redacted when MPs' claims are eventually published, the law will be broken.

In February 2008 the information tribunal had ruled that MPs' receipts should be published, a ruling upheld by the high court, in May that year, against an appeal to try to prevent disclosure of the second-home expenses claims of 14 MPs. But in July, parliament went against the court by exempting some information – MPs' addresses – from disclosure.

Tomlison said that if the redactions now went ahead an application could be made to uphold the court's ruling. "If deletions are made … the Commons [will] not have complied with the court orders."

The Commons' members estimate committee had advised that MPs should make sure that only l­imited information was made available. In notes to MPs the ­committee said releases would be confined to the name of the MP, the type of allowance, date and value of the claim, the goods or services purchased, and the identity of the supplier. The committee said: "Editing for the claims-based allowances was done on the principle that the [above] information would be made available and all other information would be removed."

MPs, the committee said, should "look out for" 14 areas where information could be removed, including all correspondence with MPs and the Commons department of resources, which includes the fees office, all notes added by Commons staff, plus other specified redactions including the dates and times of till receipts and the names of hotels and guest houses.

The deadline for the redactions was last Thursday. The committee is under pressure to publish the documents before the planned publication time of mid-July.

Robinson, the former paymaster-general, has written to Harman drawing attention to Tomlinson's view, first reported in the Coventry Telegraph. Robinson said: "It seems to me in the light of Hugh Tomlinson's statement … that if we were to resist the publication of this correspondence we would give the impression, yet again, that we were covering up. And that is the last thing we want to do in the present circumstances! This does not of course affect the necessary redaction of information regarding private individuals, which as data holders, we must protect."

Another former minister, James Plaskitt, criticised the redactions. "I don't agree with what they are doing," he told the Coventry Telegraph. "They should only redact private information that compromises our personal security or personal financial security and that of others."

A letter from Plaskitt to the fees office, in which he thanks them for spotting that he had overclaimed by £800 on the mortgage on his one-bedroom flat in London, is one of those marked for deletion by the Commons authorities.

A spokeswoman for the committee said: "The house authorities complied with the ruling in releasing the information regarding the 14 MPs named in the tribunal. Then the house decided to publicise expenses details of all MPs. These redactions are in accordance with the decision made by the MEC when it considered a publication scheme. It does not preclude further freedom of information requests."

But Heather Brooke, a campaigner from Your Right to Know, who led the freedom of information challenge, was unimpressed by this argument. "A legal precedent was set and that was why the House of Commons decided to release all the information," she said. "If it was valid for those 14 MPs it's valid for all MPs."

Brooke added: "A legal precedent was set and that was why the House of Commons [originally] decided to release all the information. The supp­ression of material causing embarrassment to MPs is in no way a legal reason to delete information."